1. Field of the Invention
The invention relates to precision measuring devices of the type utilizing sonic delay lines with a magnet movable along same and more particularly to an improved mode converter design for producing torsional pulses in the delay line.
2. Prior Art
Sonic delay lines are well known in general--e.g. U.S. Pat. Nos. 2,995,736; 3,011,136 and 3,898,555. Furthermore, their use in precision gauges has heretofore required several thin magnetostrictive (e.g. nickel) transducers--or "mode converters" as they are commonly termed--generally having one end attached to the delay line at the same axial position, but disposed at equal intervals on the periphery of the delay line for purposes of converting longitudinal stress (compression/expansion) waves into torsional waves propagating down to delay line, and vice versa. Each transducer has its other end buried in damping material after passage through a multi-loop coil of wire for generation of the stress waves or for detection of these, as the case may be.
As a result of provision for damping this other end of each transducer, the entire electronic circuit has been testable as a unit only after completion of assembly prior to transfer to inventory or just prior to shipment to the end user. Should performance problems be encountered at that point or a malfunction occur during use after shipment, a significant part of the circuitry may require disassembly, the problem isolated and the repaired or replaced members reinstalled. Such disassembly and reassembly often disturb adjustments or affect calibration with attendant need for additional operations.
Accordingly, there is yet need for further improvement in this aspect of devices of the type mentioned.